Resiliently mounted sounding board



Aug- 28, '1955 K. cAsPERsf-:N 2,760,393

RESILIENTLY MOUNTED SOUNDING BOARD Filed Aug. 3, 1951 K Nuo CASPERSEN mvENTo rz @QLMM @mi 55mm ha AT1-V5.

United States Patent RESILIENTLY MOUNTED SOUNDING BOARD Knud Caspersen, Aarhus, Denmark Application August 3, 1951, Serial No. 244,538

Claims priority, application Denmark August 9, 1950 1 Claim. (Cl. 84-192) The invention relates to sounding boards for fastening in musical instruments having a striking mechanism, such as for instance pianettes, pianinos and grand pianos, whereby it is possible to improve the formation of sound by a suitable increase of movability of the sounding board in zones in which such increase in elasticity may be desirable in order to improve the conformity between the movability of the sounding board and the frequency of the sound oscillations caused by the striking or snapping of the strings.

Generally sounding boards in the instruments in question are glued directly to the wooden frame of the instrument. Thereby the sounding board will be fixed along its entire edge and it will be difficult to obtain a suitable amount of movability particularly along the base edge of the sounding board in a small instrument with a heavily reduced sounding board surface.

It is known practice to increase the movability of the area along the edge of the sounding board by letting it rest on a bridge suspended between two points. The length of such bridge will as a matter of course be strictly limited when it is supported only at its ends, inter alia because its elasticity increases by the square towards the centre of the bridge.

It is likewise known practice to use a bridge like that mentioned above and to support it at one or more points between the ends, but this will cause dead zones along the edge through which only a minimal transmission of sound will take place. Besides, these points of support increase the rigidity and the dead zones form undesirable sonorons figures.

These defects are remedied by the present invention which relates to the fastening of sound boards in musical instruments with striking mechanism of the kind in which the sounding board is elastically suspended in relation to the framework or iron frame of the instrument by means of a list interposed between the edge of the sounding board and the framework or iron frame and fastened to the edge of the sounding board and to the frame by spacers, the spacers between the edge of the sounding board and the list along the longitudinal edge of the sounding board being offset in relation to the spacers between the list and the framework or iron frame, in such a way that the spaces formed will be offset in relation to each other. Thereby dead zones will be obviated and a materially improved eect over that of known constructions will be attained as regards timbre, hornogeneity and volume.

In the fastening of the edge of the sounding board, the offsetting of the two sets of spacers will require that the sounding board where so fastened, will at all points of fastening be elastically suspended, so that the sound vibrations of the sounding board may spread also along the edge without being stopped by rigid points.

The movability of the sounding board and its resistance against the pressure exerted by the strings at any point of the sounding board may be adjusted to the desired magnitude by the insertion of a larger or smaller number Patented Aug. 28, 1956 ICC 2 of spacers or by changing the lengths of the spacersv or the diamensions of the list interposed.

The drawing shows a section through the frame of an instrument in which the sounding board is fastened in accordance with the present invention.

Fig. 1 showing a section at right angles to the .sounding board in the longitudinal direction of the frame on line I-I in Fig. 2, and

Fig. 2 another section at right angles to the sounding board but in the transverse direction of the frame on line II-II in Fig. l.

The sounding board, l, is provided with a reinforcing list, 2. Between the sounding board, 1, and the framework or iron frame, 3, of the instrument and elastic list or bridge, 4, of resilient material, preferably a suitable wood, is interposed. The resilient list or bridge, 4, is at one side fastened to the sounding board by means of spacers, 5, of rigid or resilient material, and on the other side to the framework or iron frame of the instrument, 3, by means of other spacers, 6, which may likewise be of rigid or resilient material. By this manner of fastening the sounding board will have considerable freedom of motion in the directions indicated by the double arrow. In order that the freedom of motion may be as homogeneous as possible it is necessary to offset spacers 5 and 6 in relation to each other.

The manner of fastening described is of special importance in instruments of small dimensions, for instance, pianettes, in which the sounding board bridge due to the required length of string in connection with the small area of the sounding board will be situated very close to the lower edge of the sounding board (in grand pianos the rear edge), or in the very area in which the sounding board is subject to oscillations of low frequency demanding large fluctuations and thus great movability of the sounding board. It goes without saying that such movability cannot be obtained if the sounding board is glued to the frame and an attempt to improve conditions by reducing the thickness of the sounding board around these places will cause the sounding board to lose resonance power as regards the upper tones which are of immense importance for the timbre and the absence of which will give a furry timbre.

The manner of attachment according to the invention makes it possible to obtain the desired movability of the sounding board while maintaining its thickness, and the transmission of sound may freely take place along the entire edge of the sounding board thus suspended, so that a greater part of the sounding board may swing in resonance with the oscillations to which it is subjected. At the same time the sounding board will become to a greater extent aperiodic.

In order to prevent foreign substances from dropping down and jamming, whereby secondary sounds may be caused, the intervals between the spacers may be lled up with neutral substances, such as, for instance, wool, synthetic wool, cotton, synthetic cotton, silk, rayon, rubber, synthetic rubber or skin.

Having thus described my invention, what I claim is:

A resiliently mounted sounding-board structure for attachment to the frame of a stringed musical instrument, especially a percussion type instrument, said structure including a sounding-board proper and a highly elastic supporting composite, interposed between said soundingboard proper and said frame, said composite comprising two discrete sets of relatively short spacers and an elastic list interposed between said spacers, the two spacers positioned at each one of the opposite ends of the soundingboard lying in a single plane which is perpendicular to said sounding-board, each one of the remainder of said spacers lying in a discrete plane, all of said discrete planes extending in a direction perpendicular to the single plane of said sounding-board, all said last planes being substantially uniformly mutually spaced apart across the extent of said sounding-board, and alternate ones of said remainder of the spacers lying upon opposite sides of said list.

References Cited in the le of this patent UNITED STATES PATENTS 473,307 Fischer Apr. 19, 1892 10 4 Schleicher Iune 26, 1894 Ivers Feb. 18, 1896 Caddick Dec. 17, 1907 Johnson July 16, 1912 Hattemer Aug. 20, 1918 Virz Aug. 17, 1920 Heller Oct. 24, 1939 FOREIGN PATENTS Great Britain July 30, 1925 

